Really neat idea. I've always preferred self-teaching over group lessons but I think having a one on one session on occasion would greatly increase the rate of learning. Usually there are just a few hurdles that take most of the time. Having an expert available would remove these. Further, its always great to get a perspective based on experience.

I feel like a very simple site integrated with google calendar and video chat would suffice :)

Thanks to everyone who commented with sites that have applied similar ideas!